Differential gearbox assembly for a turbine engine

ABSTRACT

A differential gearbox assembly for a turbine engine having a fan shaft and a drive shaft. The differential gearbox assembly includes an epicyclic gear assembly coupling the fan shaft to the drive shaft. The epicyclic gear assembly includes a sun gear, a planet gear constrained by a planet carrier, and a ring gear. The sun gear is coupled to the drive shaft and the planet carrier is coupled to the fan shaft. The sun gear, the planet gear, and the ring gear all rotate about the drive shaft. The differential gearbox assembly includes an electric machine assembly that includes an input coupled to the epicyclic gear assembly. The electric machine assembly provides mechanical power to the fan shaft through the epicyclic gear assembly.

TECHNICAL FIELD

The present disclosure relates generally to differential gearboxassemblies for turbine engines.

BACKGROUND

A turbine engine generally includes a fan and a core section arranged inflow communication with one another. A gearbox assembly is coupledbetween the fan and the core section.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages will be apparent fromthe following, more particular, description of various exemplaryembodiments, as illustrated in the accompanying drawings, wherein likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

FIG. 1 is a schematic cross-sectional diagram of a turbine engine, takenalong a longitudinal centerline of the turbine engine, according to anembodiment of the present disclosure.

FIG. 2 is a schematic cross-sectional diagram of a turbine engine, takenalong a longitudinal centerline of the turbine engine, according to anembodiment of the present disclosure.

FIG. 3 is a schematic cross-sectional diagram of a turbine engine, takenalong a longitudinal centerline of the turbine engine, according to anembodiment of the present disclosure.

FIG. 4 is a schematic cross-sectional side view of a differentialgearbox assembly for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure.

FIG. 5 is a schematic cross-sectional side view of a differentialgearbox assembly for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure.

FIG. 6 is a schematic cross-sectional side view of a differentialgearbox assembly for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure.

FIG. 7 is a schematic cross-sectional side view of a differentialgearbox assembly for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure.

FIG. 8 is a schematic cross-sectional side view of a differentialgearbox assembly for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure.

FIG. 9 is a schematic cross-sectional side view of a differentialgearbox assembly for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure.

FIG. 10 is a flow diagram of an exemplary method of operating adifferential gearbox assembly of a turbine engine, according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

Additional features, advantages, and embodiments of the presentdisclosure are set forth or apparent from a consideration of thefollowing detailed description, drawings, and claims. Moreover, both theforegoing summary of the present disclosure and the following detaileddescription are exemplary and intended to provide further explanationwithout limiting the scope of the disclosure as claimed.

Various embodiments of the present disclosure are discussed in detailbelow. While specific embodiments are discussed, this is done forillustration purposes only. A person skilled in the relevant art willrecognize that other components and configurations may be used withoutdeparting from the spirit and the scope of the present disclosure.

As used herein, the terms “first,” “second,” and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.

The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows.

The terms “coupled,” “fixed,” “attached,” “connected,” and the like,refer to both direct coupling, fixing, attaching, or connecting, as wellas indirect coupling, fixing, attaching, or connecting through one ormore intermediate components or features, unless otherwise specifiedherein.

The singular forms “a,” “an,” and “the” include plural references unlessthe context clearly dictates otherwise.

As used herein, the terms “axial” refers to directions and orientationsthat extend substantially parallel to a centerline of the turbineengine. Moreover, the terms “radial” and “radially” refer to directionsand orientations that extend substantially perpendicular to thecenterline of the turbine engine. In addition, as used herein, the terms“circumferential” and “circumferentially” refer to directions andorientations that extend arcuately about the centerline of the turbineengine.

As used herein, “mechanical power,” or “mechanically powered” refers toan amount of energy transferred or converted per unit time. Mechanicalpower is the product of a force on an object and the velocity of theobject, or a product of a torque on a shaft and the angular velocity ofthe shaft.

As used herein, “electric power” refers to the rate per unit time atwhich electrical energy is transferred by an electric circuit.

The compressor section, the turbine section, and the fan may requiredifferent speeds and mechanical power to achieve greater efficiencies(e.g., improved efficiency in the conversion of kinetic energy in thefluid stream to mechanical energy in the turbine shaft). The embodimentsof the present disclosure provide for a differential gear system inwhich the fan shaft, the high pressure (HP) shaft, and the boosteroperate at different speeds using a carrier gear system. The presentdisclosure allows the individual modules (e.g., the fan shaft, the HPshaft, and the booster) to rotate at different speeds and allows thelower pressure (LP) system to rotate at higher speeds while maintainingthe speed of the fan and the booster at desired levels. The high speedLP shaft of the LP system provides torque or mechanical power to a sungear of the differential gear system that rotates at the high speed ofthe LP shaft. A carrier gear of the differential gear system is drivenby the sun gear and, in turn, drives the fan shaft at a different speedthan the LP shaft. The fan shaft and the LP shaft may rotate in the samedirection. The carrier gear is connected to a ring gear of thedifferential gear system. The ring gear is connected to the booster andis mounted to a variable stator vane (VSV) assembly of the booster. TheVSV assembly controls the flow rate to the compressor.

An electric motor is also connected to the ring gear. The electric motorcontrols a torque distribution between the booster and the fan. Forexample, during a takeoff flight mode of the turbine engine, the torquedraw from the booster may be reduced and the electric motor may add acorresponding torque to the ring gear to drive the ring gear. Anelectric generator extracts mechanical power through the differentialgear system. For example, during a cruise flight mode, a taxi flightmode, or an approach flight, the electric generator may extractmechanical power from the ring gear and generate electric power.Embodiments of the present disclosure also provide for a hybrid-electricarchitecture in which the electric motor drives the fan without corepower. In some embodiments, the electric motor and the electricgenerator may be a dual electric motor/generator.

The embodiments provided herein allow for the mechanical power to bevaried at the booster by the VSV assembly. In order to keep speedconstant, the electric motor changes the torque to the ring gear.Electric power generation can occur when either the booster or the fanreduces mechanical power, but the LP turbine keeps the same output(e.g., the LP turbine provides the same mechanical power or torquethrough the sun gear). In some embodiments, electric power input fromthe electric motor into the system may generate more horsepower (e.g.,mechanical power) for the fan through a torque increase at the boosterstage. In such embodiments, the VSV assembly is actuated to provide forthe torque increase such that the speeds do not change.

The present disclosure allows higher rotational speeds of the LPturbine, the fan, and the high-pressure turbine. Embodiments of thepresent disclosure may differentiate the speeds at transient conditions.The equal distribution of torque on the rotating components (e.g., thefan, the LP turbine, and the booster) eliminates or reduces bearingdynamic issues and shaft dynamic issues compared to turbine engineswithout the benefit of the present disclosure.

Referring now to the drawings, FIG. 1 is a schematic cross-sectionaldiagram of a turbine engine 10, taken along a longitudinal centerline 12of the turbine engine 10, according to an embodiment of the presentdisclosure. As shown in FIG. 1 , the turbine engine 10 defines an axialdirection A (extending parallel to a longitudinal centerline 12 providedfor reference) and a radial direction R that is normal to the axialdirection A. In general, the turbine engine 10 includes a fan section 14and a core turbine engine 16 disposed downstream from the fan section14.

The core turbine engine 16 depicted generally includes an outer casing18 that is substantially tubular and defines an annular inlet 20. Asschematically shown in FIG. 1 , the outer casing 18 encases, in serialflow relationship, a compressor section including a low pressure (LP)compressor or a booster 22 followed downstream by a high pressure (HP)compressor 24, a combustion section 26, a turbine section including ahigh pressure (HP) turbine 28 followed downstream by a low pressure (LP)turbine 30, and a jet exhaust nozzle section 32. A high pressure (HP)shaft 34 drivingly connects the HP turbine 28 to the HP compressor 24 torotate the HP turbine 28 and the HP compressor in unison. The compressorsection, the combustion section 26, the turbine section, and the jetexhaust nozzle section 32 together define a core air flowpath.

For the embodiment depicted in FIG. 1 , the booster 22 includes aplurality of stages. For example, the booster 22 includes a firstbooster stage 22 a, also referred to as a fan booster, and a secondbooster stage 22 b, also referred to as an LP turbine booster. A lowpressure (LP) shaft 36, or drive shaft, drivingly connects the LPturbine 30 to the second booster stage 22 b to rotate the LP turbine 30and the second booster stage 22 b in unison. The first booster stage 22a includes a plurality of blades 23 and a plurality of variable statorvanes (VS V) The VSVs 25 include a first stage of VSVs 25 positionedupstream of the plurality of blades 23. The VSVs may also include asecond stage of VSVs 25 positioned downstream of the plurality of blades23. Each VSV 25 is rotatable about a pitch axis P by virtue of the VSVsbeing operatively coupled to an actuation member configured tocollectively vary the pitch of the VSVs in unison. The plurality ofblades 23 are rotatable about the longitudinal centerline 12 via abooster shaft 27 that is mechanically powered by the LP shaft 36 acrossa differential gearbox assembly 46, as detailed further below. Thedifferential gearbox assembly 46 includes an epicyclic gear assembly inwhich a sun gear, a planet carrier, and a ring gear all rotate withrespect to the longitudinal centerline 12, as detailed further below.The differential gearbox assembly 46 includes a plurality of gears foradjusting the rotational speed of the booster shaft 27 and, thus, thefirst booster stage 22 a relative to the LP shaft 36 to a more efficientbooster speed. In some examples, the booster 22 includes a singlebooster stage connected to the differential gearbox assembly 46. In someexamples, the booster 22 includes a plurality of booster stagesconnected to the differential gearbox assembly 46.

The fan section 14 includes a fan 38 having a plurality of fan blades 40coupled to a disk 42 in a spaced apart manner. As depicted in FIG. 1 ,the fan blades 40 extend outwardly from the disk 42 generally along theradial direction R. The fan blades 40 and the disk 42 are togetherrotatable about the longitudinal centerline 12 via a fan shaft 45 thatis mechanically powered by the drive shaft (e.g., the LP shaft 36)across the differential gearbox assembly 46, as detailed further below.While the drive shaft is depicted as the LP shaft 36, the drive shaftmay be the HP shaft 36 in some examples. The plurality of gears of thedifferential gearbox assembly 46 adjusts the rotational speed of the fanshaft 45 and, thus, the fan 38 relative to the LP shaft 36 to a moreefficient rotational fan speed.

The differential gearbox assembly 46 includes an electric machineassembly 48 operable with the differential gearbox assembly 46, asdetailed further below. The electric machine assembly 48 includes astator 51 and a rotor 53. The stator 51 and the rotor 53 are annularabout the LP shaft 36 (e.g., about the longitudinal centerline 12) andthe electric machine assembly 48 is an annular drive system. Forexample, the stator 51 and the rotor 53 are annular rings and areconcentric with respect to each other. The rotor 53 is disposed radiallywithin the stator 51. In some examples, the stator 51 is disposedradially within the rotor 53.

The stator 51 is fixedly mounted to, for example, the outer casing 18via one or more linkages. The rotor 53 is coupled to a gear (e.g., aring gear) of the differential gearbox assembly 46, for example, by ageared coupling, a spline coupling, a bolt, or the like. In this way,the rotor 53 is rotatable by the gear of the differential gearboxassembly 46, and the gear of the differential gearbox assembly 46 isrotatable by the rotor 53, allowing mechanical power or torque to betransferred between the electric machine assembly 48 and the gear of thedifferential gearbox assembly 46, as detailed further below. The rotor53 is rotatable by the gear of the differential gearbox 46 at the samespeed as the gear. Generally, the electric machine assembly 48, togetherwith the differential gearbox assembly 46, allows the turbine engine 10to operate with improved efficiency, as the operating speeds of the LPshaft 36, the first booster stage 22 a, and the fan 38 may beindependently changed to improve stability and efficiency for aparticular operating mode of the turbine engine 10. More specifically,the operating speed of the first booster stage 22 a may be controlled toimprove the efficiency of the first booster stage 22 a across transientspeeds of the LP shaft 36. For example, the electric machine assembly 48facilitates torque transfer between the first booster stage 22 a and thefan 38, as detailed further below. In this way, the electric machineassembly 48 and the differential gearbox assembly 46 allow for optimallycontrolling the torque to the first booster stage 22 a and the fan 38 atvarious mission cycles (e.g., takeoff, climb, cruise, descent, taxi, andapproach).

Referring still to the exemplary embodiment of FIG. 1 , the fan section14 includes an annular fan casing or a nacelle 50 that circumferentiallysurrounds the fan 38 and/or at least a portion of the core turbineengine 16. The nacelle 50 is supported relative to the core turbineengine 16 by a plurality of circumferentially spaced outlet guide vanes52. Moreover, a downstream section 54 of the nacelle 50 extends over anouter portion of the core turbine engine 16 to define a bypass airflowpassage 56 therebetween.

During operation of the turbine engine 10, a volume of air 58 enters theturbine engine 10 through an inlet of the nacelle 50 and/or the fansection 14. As the volume of air 58 passes across the fan blades 40, afirst portion of the air 58 as indicated by arrow 62 is directed orrouted into the bypass airflow passage 56, and a second portion of theair 58 as indicated by arrow 64 is directed or is routed into theupstream section of the core air flowpath, or, more specifically, intothe annular inlet 20 of the booster 22. The ratio between the firstportion of air 62 and the second portion of air 64 is commonly known asa bypass ratio. The pressure of the second portion of air 64 is thenincreased as the second portion of air 64 is routed through the HPcompressor 24 and into the combustion section 26, where the highlypressurized air is mixed with fuel and burned to provide combustiongases 66.

The combustion gases 66 are routed into the HP turbine 28 and expandedthrough the HP turbine 28 where a portion of thermal and/or of kineticenergy from the combustion gases 66 is extracted via sequential stagesof HP turbine stator vanes that are coupled to the outer casing 18 andHP turbine rotor blades 70 that are coupled to the HP shaft 34, thuscausing the HP shaft 34 to rotate, thereby supporting operation of theHP compressor 24. The combustion gases 66 are then routed into the LPturbine 30 and expanded through the LP turbine 30. Here, a secondportion of thermal and kinetic energy is extracted from the combustiongases 66 via sequential stages of the LP turbine stator vanes that arecoupled to the outer casing 18 and the LP turbine rotor blades 74 thatare coupled to the LP shaft 36, thus, causing the LP shaft 36 to rotate.This thereby supports operation of the booster 22 and rotation of thefan 38 via the differential gearbox assembly 46, as detailed furtherbelow.

The combustion gases 66 are subsequently routed through the jet exhaustnozzle section 32 of the core turbine engine 16 to provide propulsivethrust. Simultaneously, the pressure of the first portion of air 62 issubstantially increased as the first portion of air 62 is routed throughthe bypass airflow passage 56 before being exhausted from a fan nozzleexhaust section 76 of the turbine engine 10, also providing propulsivethrust. The HP turbine 28, the LP turbine 30, and the jet exhaust nozzlesection 32 at least partially define a hot gas path 78 for routing thecombustion gases 66 through the core turbine engine 16.

The turbine engine 10 depicted in FIG. 1 is by way of example only. Inother exemplary embodiments, the turbine engine 10 may have any othersuitable configuration. For example, in other exemplary embodiments, thefan 38 may be configured in any other suitable manner (e.g., as a fixedpitch fan) and further may be supported using any other suitable fanframe configuration. Moreover, it should be appreciated that, in otherexemplary embodiments, any other suitable number or configuration ofcompressors, turbines, shafts, or a combination thereof may be provided.In still other exemplary embodiments, aspects of the present disclosuremay be incorporated into any other suitable turbine engine, such as, forexample, turbofan engines, propfan engines, turbojet engines, and/orturboshaft engines.

FIG. 2 is a schematic cross-sectional diagram of a turbine engine 210,taken along a longitudinal centerline 12 of the turbine engine 210,according to an embodiment of the present disclosure. The embodiment ofFIG. 2 includes many of the same or similar components and functionalityas the embodiment shown in FIG. 1 . The same reference numeral is usedfor the same or similar components in these embodiments, and a detaileddescription of these components and functionality is omitted here. Somereference numerals have been removed for clarity.

In the embodiment of FIG. 2 , the turbine engine 210 includes a propfanengine, also referred to as an open-fan engine or as an unducted fanengine. In this way, the turbine engine 210 of FIG. 2 does not include anacelle 50 covering the fan 38. Open-fan engines, such as the turbineengine 210, provide for ultra-high bypass ratios, and thus provide forimproved propulsive efficiency as compared to ducted fan engines (e.g.,turbofan engines or turboprop engines). A core turbine engine 216 of theturbine engine 210 may be substantially the same as the core turbineengine 16 of the turbine engine 10. A fan section 214 of the turbineengine 210 includes a plurality of fans 238 including a first fan 238 aand a second fan 238 b.

The first fan 238 a is substantially to the fan 38 of FIG. 1 andincludes a plurality of first fan blades 240 a coupled to a first disk242 a in a spaced apart manner. The second fan 238 b includes aplurality of second fan blades 240 b coupled to a second disk 242 b in aspace apart manner. The second fan 238 b is located downstream of thefirst fan 238 a. The first fan blades 240 a and the first disk 242 a aretogether rotatable about the longitudinal centerline 12 via a first fanshaft 245 a that is mechanically powered by the LP shaft 36 across adifferential gearbox assembly 246, similar to the embodiment of FIG. 1 .The second fan blades 240 b and the second disk 242 b are togetherrotatable about the longitudinal centerline 12 via a second fan shaft245 b that is mechanically powered by the LP shaft 36 across thedifferential gearbox assembly 246, as detailed further below. The secondfan shaft 245 b is counter-rotating to the first fan shaft 245 a.

The plurality of gears of the differential gearbox assembly 46 adjuststhe rotational speed of the first fan shaft 245 a and, thus, the firstfan 238 a relative to the LP shaft 36 to a more efficient rotational fanspeed of the first fan 238 a. Similarly, the plurality of gears of thedifferential gearbox assembly 246 adjusts the rotational speed andadjusts the direction of rotation of the second fan shaft 245 b and,thus, the second fan 238 b relative to the LP shaft 36 to a moreefficient rotational fan speed of the second fan 238 b. In this way, thefirst fan 238 a and the second fan 238 b are counter-rotating, whichprovides a higher propulsive efficiency as compared tonon-counter-rotating fans. In the embodiment of FIG. 2 , the second fanshaft 245 b, the first booster stage 22 a, and the electric machineassembly 48 are connected to a ring gear 284 of the differential gearboxassembly 246, as detailed further below.

FIG. 3 is a schematic cross-sectional diagram of a turbine engine 310,taken along a longitudinal centerline 12 of the turbine engine 310,according to an embodiment of the present disclosure. The embodiment ofFIG. 3 includes many of the same or similar components and functionalityas the embodiment shown in FIG. 1 . The same reference numeral is usedfor the same or similar components in these two embodiments, and adetailed description of these components and functionality is omittedhere. Some reference numerals have been removed for clarity.

In the embodiment of FIG. 3 , the turbine engine 310 includessubstantially the same turbine engine 10 as the embodiment of FIG. 1 .For example, the turbine engine 310 includes a core turbine engine 316and a differential gearbox assembly 346 that include similar componentsof the core turbine engine 16 and the differential gearbox assembly 46,detailed above. The turbine engine 310, however, does not include afirst booster stage connected to the differential gearbox assembly 346.Rather, the turbine engine 310 includes a stationary structure 349disposed upstream of a booster 322. The stationary structure 349connects an electric machine assembly 348 and/or connects thedifferential gearbox assembly 346 to the outer casing 18. Thus, in theembodiment FIG. 3 , the electric machine assembly 348 allows the turbineengine 310 to operate with improved efficiency, as the operating speedsof the LP shaft 36 and the fan 38 may be independently changed toimprove stability and efficiency. More specifically, the operating speedof the fan 38 may be controlled to improve the efficiency of the fan 38across transient speeds of the LP shaft 36. For example, the electricmachine assembly 348 facilitates torque transfer between the LP shaft 36and the fan 38, as detailed further below. In this way, the electricmachine assembly 348 and the differential gearbox assembly 46 allow foroptimally controlling the torque to the fan 38 at various mission cycles(e.g., takeoff, climb, cruise, descent, taxi, and approach).

The electric machine assembly 348 includes a stator 351 and a rotor 353.The electric machine assembly 348 is similar to the electric machineassembly 48 of FIG. 1 and is annular about the LP shaft 36. The stator351 is fixedly mounted to, for example, the outer casing 18 via one ormore linkages. The rotor 353 is coupled to a gear of the differentialgearbox assembly 346, as detailed above. In this way, the rotor 353 isrotatable by the gear of the differential gearbox assembly 346, and thegear of the differential gearbox assembly 346 is rotatable by the rotor353, allowing mechanical power or torque to be transferred between theelectric machine assembly 348 and the gear of the differential gearboxassembly 346, as detailed further below.

FIG. 4 is a schematic cross-sectional side view of a differentialgearbox assembly 446 for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure. The differential gearbox assembly 446 may beemployed in the turbine engine 10 of FIG. 1 or in the turbine engine 210of FIG. 2 . That is, the differential gearbox assembly 446 may couplethe LP shaft 36 to the fan 38 and to the first booster stage 22 a (FIG.1 ) or may couple the LP shaft 36 to the first fan 238 a, to the secondfan 238 b, and to the first booster stage 22 a (FIG. 2 ). Thedifferential gearbox assembly 446 includes an epicyclic gear assembly479 including a sun gear 480, a plurality of planet gears 482 (only oneof which is visible in FIG. 4 ), and a ring gear 484. For clarity, onlya portion of the gears is shown (e.g., the sun gear 480 includes aportion below the LP shaft 36 and the ring gear 484 is annular andencircles the LP shaft 36). A planet carrier 486 constrains theplurality of planet gears 482 to rotate around the sun gear 480 insynchronicity while enabling each planet gear of the plurality of planetgears 482 to rotate about its own axis. For clarity, only a portion ofthe gears is shown. A housing 489 may enclose the differential gearboxassembly 446. The housing 489 includes a stationary component such thatthe housing 489 does not rotate. The planet carrier 486 is coupled tothe fan 38 (FIG. 1 ) or to the first fan 238 a (FIG. 2 ) and rotateswith the plurality of planet gears 482 in order to drive rotation of thefan 38 (FIG. 1 ) or the first fan 238 a (FIG. 2 ) about the longitudinalcenterline 12 (FIGS. 1 and 2 ). Radially outwardly of the plurality ofplanet gears 482, and intermeshing therewith, is the ring gear 484. Inthe differential gearbox assembly 446, the ring gear 484, the planetcarrier 486, and the plurality of planet gears 482 each rotate about thelongitudinal centerline 12 (FIGS. 1 and 2 ).

The LP shaft 36 is connected to the sun gear 480, the fan shaft 45 isconnected to the planet carrier 486, and the booster shaft 27 isconnected to the ring gear 484. In this way, the LP shaft 36 and the sungear 480 are rotatable together, the fan shaft 45 and the planet carrier486 are rotatable together, and the booster shaft 27 and the ring gear484 are rotatable together. In some examples, the second fan shaft 245 b(FIG. 2 ) is also connected to the ring gear 484 such that the secondfan shaft 245 b and the ring gear 484 are also rotatable together.

The differential gearbox assembly 446 includes an electric machineassembly 448. The electric machine assembly 448 includes an electricmotor 490 and an electric generator 492. In some examples, the electricmotor 490 and the electric generator 492 may together form a singlecomponent of the electric machine assembly 448 such that the electricmachine assembly 448 is a dual electric motor/electric generator (asshown in FIG. 4A). In some examples, the electric motor 490 and theelectric generator 492 may form separate components of the electricmachine assembly 448, as detailed further below. The electric machineassembly 448 of FIG. 4 is an axial electric machine, also referred to asa compact drive system, such that the stator and the rotor of theelectric machine assembly 448 are located inside a housing and are notvisible in the view of FIG. 4 . In this way, the electric machineassembly 448 is located at a discrete location within turbine engine 410and the electric machine assembly 448 is not annular about the LP shaft36. The electric machine assembly 448 includes an input 455. The input455 is coupled to a rotating component of the differential gearboxassembly 446, such as to the ring gear 484. In this way, the ring gear484 is coupled to both the booster 22 (e.g., the first booster stage 22a) and the electric machine assembly 448 (and the second fan 238 b ofFIG. 2 ). The input 455 includes a shaft 451 and a gear 453. The shaft451 is coupled to the rotor internally to the electric machine assembly448 such that rotation of the shaft 451 rotates the rotor and the rotorrotates with respect to the stator (also located internally to theelectric machine assembly 448). The shaft 451 is coupled to the gear 453and the gear 453 intermeshes with the ring gear 484. In this way, theinput 455 is rotatable by the ring gear 484, and the ring gear 484 isrotatable by the input 455, allowing mechanical power or torque to betransferred between the electric machine assembly 448 and the ring gear484. The gear 453 includes a smaller diameter than the ring gear 484.Accordingly, the shaft 451 rotates faster than the ring gear 484.

The electric machine assembly 448 may have any suitable configuration.For example, the electric machine assembly 448 may be configured in anysuitable manner for converting mechanical power to electrical power, orelectrical power to mechanical power. For example, the electric machineassembly 448 may be configured as an asynchronous or an inductionelectric machine operable to generate or to utilize alternating current(AC) electric power. Alternatively, the electric machine assembly 448may be configured as a synchronous electric machine operable to generateor to utilize AC electric power or direct current (DC) electric power.In such a manner, the stator, the rotor, or both, may generally includeone or more of a plurality of coils or winding arranged in any suitablenumber of phases, one or more permanent magnets, one or moreelectromagnets, etc.

The embodiments detailed herein may use an annular drive system electricmachine (e.g., the electric machine assembly 48 of FIG. 1 ) or a compactdrive system (e.g., the electric machine assembly 448 of FIG. 4 ).Selection of the electric machine assembly (e.g., annular drive systemor compact drive system) may be based on a balance of size, weight,electric power requirements, etc. For example, annular drive systemsincludes a rotor and a stator that have larger diameters than the rotorsand stators of compact drive systems. In this way, a single annulardrive system generates or outputs more electric power than a compactdrive system. A compact drive system, however, requires less spacewithin a particular turbine engine than the annular drive system andthus provides more weight savings compared to an annular drive system.In some examples, a plurality of compact drive systems may be used andmay be coupled to the ring gear 484 at various circumferential locationsto match the electric power capabilities of a single annular drivesystem.

In certain exemplary embodiments, the electric machine assembly 448 maybe operated as the electric generator 492, such that mechanical powermay be transferred from the ring gear 484 to the rotor via the input 455of the electric machine assembly 448, with the electric machine assembly448 converting such mechanical power to electrical power. The electricmachine assembly 448 may further store such electric power (e.g., tocharge a battery pack, or for any other suitable purpose). Further, inother exemplary aspects, however, the electric machine assembly 448 maybe operated as the electric motor 490, converting electrical power tomechanical power, rotating the rotor via the input 455 of the electricmachine assembly 448 in a circumferential direction and driving the ringgear 484 via the input 455. In such a manner, the electric machineassembly 448 rotates the first booster stage 22 a, the fan 38, or both.The electric machine assembly 448 may receive electrical power from theelectric generator 492 during such operations. In some examples, theelectric machine assembly 448 drives the ring gear 484 to rotate thefirst booster stage 22 a and the second fan 238 b (FIG. 2 ).

In operation, the LP shaft 36 rotates at a high speed and providestorque or mechanical power to the sun gear 480 at the high speed. Thesun gear 480 drives the planet carrier 486 (e.g., through the pluralityof planet gears 482), and the planet carrier 486 drives the fan 38 at adifferent speed than the LP shaft 36. The planet carrier 486 isconnected to the ring gear 484, and the ring gear 484 is connected tothe first booster stage 22 a and to the electric machine assembly 448,as detailed above. In some examples, the ring gear 484 is also drivesthe second fan 238 b (FIG. 2 ). Mechanical power of the LP shaft 36 isprovided as an input to the differential gearbox assembly 446 via thesun gear 480. The mechanical power of the LP shaft 36 is provided to thefan 38 via the planet carrier 486. The mechanical power of LP shaft 36is also provided to the first booster stage 22 a and to the electricmachine assembly 448 (and to the second fan 238 b of FIG. 2 ) via thering gear 484. In this way, torque is transferred from the LP turbine 30(FIGS. 1 to 3 ) to the sun gear 480 through the LP shaft 36. The torqueis transferred from the sun gear 480 through the planet carrier 486 tothe fan 38 via the fan shaft 45. The torque is also transferred from thesun gear 480 through the ring gear 484 to the booster 22 (e.g., thefirst booster stage 22 a) via the booster shaft 27. The mechanical powerand the torque provided by the ring gear 484 is split between the firstbooster stage 22 a and the electric machine assembly 448 (and the secondfan 238 b of FIG. 2 ).

The mechanical power or the torque split between the first booster stage22 a and the electric machine assembly 448 is varied at the firstbooster stage 22 a by modulating the VSVs 25. For example, the VSVs 25may be actuated to rotate about the pitch axis P to provide an incidenceangle of the VSVs 25 to control an angle of the air 64 flow to theplurality of blades 23 of the first booster stage 22 a. In this way, themechanical power draw or the torque draw from the first booster stage 22a is a function of the incidence angle of the VSVs 25. For example, anoptimum incidence angle of the VSVs 25 may provide a maximum mechanicalpower or a maximum torque draw from the first booster stage 22 a for agiven speed of the first booster stage 22 a.

In a first operating mode, the electric motor 490 of the electricmachine assembly 448 drives the ring gear 484 to control a torquedistribution for the first booster stage 22 a and the fan 38 (e.g., thefan shaft 45). The electric motor 490 may provide electric power inputthrough the ring gear 484 to generate more horsepower (e.g., mechanicalpower) at the fan 38 through a torque increase at the first boosterstage 22 a. For example, the electric motor 490 changes the torque ofthe ring gear 484, while the VSVs 25 are actuated to control theincidence angle to ensure the speed of the ring gear 484 remainsconstant.

In a second operating mode, the electric generator 492 of the electricmachine assembly 448 generates electric power. For example, the firstbooster stage 22 a may reduce mechanical power, while the mechanicalpower provided by the LP shaft 36 remains constant. The VSVs 25 areactuated to change the incidence angle in order to reduce the mechanicalpower of the first booster stage 22 a. The mechanical power of the LPshaft 36 that is no longer going to the first booster stage 22 a (e.g.,due to the reduced mechanical power of the first booster stage 22 a) isprovided to the electric generator 492 through the ring gear 484. Inthis way, the electric generator 492 of the electric machine assembly448 generates and stores electric power, as detailed above.

In some examples, the first operating mode is a first flight mode andthe second operating mode is a second flight mode. The first flight modeand the second flight mode include a mission cycle of the turbine engine10, 210, 310. The mission cycle may include, for example, a takeoffflight mode, a climb flight mode, a cruise flight mode, a step changeflight mode, a descent flight mode, a landing flight mode, a taxi flightmode, or the like. The second flight mode may be different than thefirst flight mode. In some examples, the first flight mode, and, thus,the first operating mode, includes the takeoff flight mode and/or thedescent flight mode. In this way, the electric motor 490 of the electricmachine assembly 448 drives the ring gear 484, as detailed above, duringthe takeoff flight mode and/or during the descent flight mode. In someexamples, the second flight mode, and, thus, the second operating mode,includes the cruise flight mode and/or the taxi flight mode. In thisway, the electric generator 492 of the electric machine assembly 448generates electric power, as detailed above, during the cruise flightmode and/or during the taxi flight mode.

FIG. 5 is a schematic side cross-sectional view of a differentialgearbox assembly 546 for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure. The differential gearbox assembly 546 includes manyof the same components and the same functionality as the differentialgearbox assembly 446. The differential gearbox assembly 546 includes anelectric machine assembly 548 connected therewith. The electric machineassembly 548 includes the electric motor 490 and an electric generator592. The electric machine assembly 548 includes substantially the samefunctionality as the electric machine assembly 448, detailed above. Forexample, the electric machine assembly 548 is a compact drive system. Inthe embodiment of FIG. 5 , the electric generator 592 is a separatecomponent from the electric motor 490. The electric generator 592 iscoupled to the LP shaft 36. For example, the electric generator 592includes an input 555. The input 555 includes a shaft 551 and a gear553. The shaft 553 coupled to the gear 553 and the gear 553 isintermeshed with the LP shaft 36. In this way, the electric generator592 generates electric power directly from the mechanical power of theLP shaft 36. For example, the torque from the LP shaft 36 is transferreddirectly to the electric generator 592 through the input 555.

FIG. 6 is a schematic cross-sectional side view of a differentialgearbox assembly 646 for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure. The differential gearbox assembly 646 may beemployed in the turbine engine 310 of FIG. 3 . In the embodiment of FIG.6 , the differential gearbox assembly 646 includes many of the samecomponents and functionality of the differential gearbox assembly 446,detailed above. The differential gearbox assembly 646, however, is notcoupled to a first booster stage 22 a of the booster 22. In this way, aring gear 484 of an epicyclic gear assembly 679 of the differentialgearbox assembly 646 is coupled to an electric machine assembly 648, butis not coupled to the booster 322. A housing 689 may enclose thedifferential gearbox assembly 646. The electric machine assembly 648includes an electric motor 690 and electric generator 692, similar tothe embodiment of FIG. 4 . For example, the electric machine assembly648 is a compact drive system and includes a shaft 651 and a gear 653.

In operation, the LP shaft 36 rotates at high speed and provides torqueor mechanical power to the sun gear 480 at the high speed. The sun gear480 drives the planet carrier 486 (e.g., through the plurality of planetgears 482), and the planet carrier 486 drives the fan 38 at a differentspeed than the LP shaft 36. The planet carrier 486 is connected to thering gear 684, and the ring gear 684 is connected to the electricmachine assembly 648, as detailed above. Mechanical power of the LPshaft 36 is provided as an input to the differential gearbox assembly646 via the sun gear 480. The mechanical power of the LP shaft 36 isprovided to the fan 38 via the planet carrier 486. The mechanical powerof LP shaft 36 is also provided to the electric machine assembly 648 viathe ring gear 684. In this way, torque is transferred from the LPturbine 30 (FIGS. 1 to 3 ) to the sun gear 480 through the LP shaft 36.The torque is transferred from the sun gear 480 through the planetcarrier 486 to the fan via the fan shaft 45. The torque is alsotransferred from the sun gear 480 through the ring gear 684 to theelectric machine assembly 648.

In a first operating mode, the electric motor 690 of the electricmachine assembly 648 drives the ring gear 684 to control a torquedistribution for the fan 38 (e.g., the fan shaft 45). The electric motor490 may provide electric power input through the ring gear 684 togenerate more horsepower (e.g., mechanical power) at the fan 38, asdetailed above. Thus, the electric motor 490 provides additionalmechanical power to the fan 38 through the ring gear 684. In a secondoperating mode, the electric generator 492 of the electric machineassembly 648 generates and stores electric power, as detailed above. Forexample, mechanical power at the fan 38 is reduced and the mechanicalpower provided by the LP shaft 36 remains constant. The remainingmechanical power from the LP shaft 36 is provided to the electricgenerator 492 via the ring gear 684 to generate electric power, asdetailed above.

FIG. 7 is a schematic cross-sectional side view of the differentialgearbox assembly 746 for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure. The differential gearbox assembly 746 includes manyof the same components and the same functionality as the differentialgearbox assembly 646. The differential gearbox assembly 746 includes anelectric machine assembly 748 connected therewith. The electric machineassembly 748 includes the electric motor 690 and an electric generator792. The electric machine assembly 748 includes substantially the samefunctionality as the electric machine assembly 648, detailed above. Inthe embodiment of FIG. 7 , however, the electric generator 792 is aseparate component from the electric motor 690. The electric generator792 is coupled to the LP shaft 36. For example, the electric generator792 includes an input 755. The input 755 includes a shaft 751 and a gear753. The shaft 751 is coupled to the gear 753 and the gear 753intermeshes with the LP shaft 36. In this way, the electric generator792 generates electric power directly from the mechanical power of theLP shaft 36.

FIG. 8 is a schematic side cross-sectional view of a differentialgearbox assembly 846 for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure. The differential gearbox assembly 846 may beemployed in the turbine engine 10 of FIG. 1 or in the turbine engine 210of FIG. 2 . In the embodiment of FIG. 8 , the differential gearboxassembly 846 includes many of the same components and functionality ofthe differential gearbox assembly 446. For example, the differentialgearbox 846 includes an epicyclic gear assembly 879. In FIG. 8 , anelectric machine assembly 848 is coupled to a planet carrier 886. Inthis way, an input 855 of the electric machine assembly 848 is coupledto the planet carrier 886. The input 855 includes a shaft 851 and a gear853, similar to the embodiment of FIG. 4 . The gear 853, however, isintermeshed with the planet carrier 886. Thus, the electric machineassembly 848 is not connected to a ring gear 884 in the embodiment ofFIG. 8 .

In operation, mechanical power of the LP shaft 36 is provided as aninput to the differential gearbox assembly 846 via the sun gear 480, asdetailed above. The mechanical power of the LP shaft 36 is provided tothe fan 38 and to the electric machine assembly 848 via the planetcarrier 886. The mechanical power of LP shaft 36 is also provided to thefirst booster stage 22 a via the ring gear 884. The mechanical power orthe torque split between the first booster stage 22 a and the electricmachine assembly 848 is varied at the first booster stage 22 a bymodulating the VSVs 25, as detailed above.

In a first operating mode, an electric motor 890 of the electric machineassembly 848 drives the planet carrier 886 to control a torquedistribution for the first booster stage 22 a (and the second fan 238 bof FIG. 2 ) and the fan 38 (e.g., the fan shaft 45) via the ring gear884. The electric motor 890 may provide electric power input through theplanet carrier 886 to generate more horsepower (e.g., mechanical power)at the fan 38 through a torque increase at the first booster stage 22 a.For example, the electric motor 890 changes the torque of the planetcarrier 886, and, thus, to the ring gear 884, while the VSVs 25 areactuated to control the incidence angle to ensure the speed of the ringgear 884 remains constant.

In a second operating mode, the electric generator 892 of the electricmachine assembly 848 generates electric power. For example, the fan 38may reduce mechanical power, while the mechanical power provided by theLP shaft 36 remains constant. The mechanical power of the LP shaft 36that is no longer going to the fan 38 (e.g., due to the reducedmechanical power of the fan 38) is provided to the electric generator892 through the planet carrier 886. In this way, the electric generator892 of the electric machine assembly 848 generates and stores electricpower, as detailed above.

FIG. 9 is a schematic side cross-sectional view of a differentialgearbox assembly 946 for a turbine engine, taken along a longitudinalcenterline of the turbine engine, according to an embodiment of thepresent disclosure. The differential gearbox assembly 946 may beemployed in the turbine engine 10 of FIG. 1 , in the turbine engine 210of FIG. 2 , or in the turbine engine 310 of FIG. 3 . In the embodimentof FIG. 9 , the differential gearbox assembly 946 includes many of thesame components and functionality of the differential gearbox assembly746. For example, the differential gearbox assembly 946 includes anepicyclic gear assembly 979.

In the embodiment of FIG. 9 , the differential gearbox assembly 946 iscoupled to an electric machine assembly 948. The electric machineassembly 948 includes an electric motor 990 and the electric generator792. The electric generator 792 is a separate component from theelectric motor 990. The electric generator 792 is a compact drive systemand is coupled to the LP shaft 36. In this way, the electric generator792 generates electric power directly from the mechanical power of theLP shaft 36. The electric motor 990 is an annular drive system. Thus,the electric motor 990 includes an input 955 that includes a stator 951and a rotor 953 that are annular about the LP shaft 36. The electricmotor 990 is considered a reverse motor in that the stator 951 iscoupled to a static component of the differential gearbox assembly 946.For example, the stator 951 may be coupled to a housing 989. The stator951 may include a plurality of windings that receive electric power froma power source (e.g., the electric generator 792). The plurality ofwindings of the stator 951 may be mounted to the housing 989. The rotor953 includes one or more permanent magnets on a ring gear 984. Forexample, the rotor 753 may be integral with the ring gear 984. In thisway, the electric motor 990 is a permanent magnet motor. Thus, the rotor953 is rotatable with the ring gear 984. The stator 951 imparts anelectromagnetic force that causes the rotor 953 to rotate, thus, causingthe ring gear 984 to rotate. In this way, mechanical power or torque istransferred between the electric machine assembly 948 and the ring gear984, as detailed above.

FIG. 10 is a flow diagram of an exemplary method 1000 of operating adifferential gearbox assembly of a turbine engine, according to anembodiment of the present disclosure. While the method 1000 is describedwith reference to the differential gearbox assembly 446 of the turbineengine 10, the method 1000, of course, may be performed by any of thedifferential gearbox assemblies and turbine engines described herein.

In step 1005, the method 1000 includes transferring torque through theLP shaft 36 from the LP turbine 30 to the sun gear 480. The LP turbine30 is driven with the combustion gases 66, as detailed above. Forexample, the LP shaft 36 rotates and provides torque and mechanicalpower to the sun gear 480.

In step 1010, the method 1000 includes transferring the torque from thesun gear 480 through the planet carrier 486 to the fan shaft 45. Forexample, the planet carrier 486 is driven by the sun gear 480 such thatthe fan shaft 45 rotates, as detailed above. In this way, the fan shaft45 rotates the fan 38.

In step 1015, the method 1000 includes transferring the torque from thesun gear 480 through the ring gear 484 to the booster shaft 27. In thisway, the booster shaft 27 rotates the booster 22. For example, thebooster shaft 27 rotates the first booster stage 22 a.

In step 1020, the method 1000 includes splitting the torque between thebooster shaft 27 and the electric machine assembly 448. Such anarrangement allows the booster shaft 27, the fan shaft 45, and the LPshaft 36 to rotate at different speeds.

In some examples, the electric machine assembly 448 drives the ring gear484 to control a distribution of the torque between the booster shaft 27and the fan shaft 45. In some examples, the electric machine assembly448 drives the planet carrier 486 to control the distribution of thetorque between the booster shaft 27 and the fan shaft 45. The electricmachine assembly 448 provides an electric power input to thedifferential gearbox assembly in a first operating mode of the turbineengine, as detailed above. The electric machine assembly 448 generateselectric power at the electric machine assembly in a second operatingmode of the turbine engine, as detailed above. In some examples, thetorque to the booster shaft 27 is reduced and the torque to the electricmachine assembly 448 is increased. The torque to the booster shaft 27 isreduced by actuating the plurality of VSVs 25, as detailed above.

The embodiments of the present disclosure detailed herein provide forhigher rotational speeds of the LP turbine, the fan, and thehigh-pressure turbine as compared to turbine engines without the benefitof the present disclosure. Embodiments of the present disclosure maydifferentiate the speeds at transient conditions (e.g., during variousmission cycles of the turbine engine). The equal distribution of torqueon the rotating components (e.g., the fan, the LP turbine, or thebooster) eliminates or reduces bearing dynamic issues and shaft dynamicissues compared to turbine engines without the benefit of the presentdisclosure.

Further aspects of the present disclosure are provided by the subjectmatter of the following clauses.

A differential gearbox assembly for a turbine engine that includes a fanshaft and a drive shaft. The differential gearbox assembly includes anepicyclic gear assembly coupling the fan shaft to the drive shaft. Theepicyclic gear assembly includes a sun gear, a planet gear constrainedby a planet carrier, and a ring gear. The sun gear is coupled to thedrive shaft and the planet carrier is coupled to the fan shaft. The sungear, the planet gear, and the ring gear all rotate about the driveshaft. The differential gearbox assembly includes an electric machineassembly that includes an input coupled to the epicyclic gear assembly.The electric machine assembly provides mechanical power to the fan shaftthrough the epicyclic gear assembly.

The differential gearbox assembly of the preceding clause, the turbineengine including a booster shaft, and the ring gear being coupled to thebooster shaft. The differential gearbox assembly splits a torque betweenthe booster shaft and the electric machine assembly.

The differential gearbox assembly of any preceding clause, thedifferential gearbox assembly transferring a torque from the LP shaft tothe electric machine assembly.

The differential gearbox assembly of any preceding clause, thedifferential gearbox transferring the torque from the LP shaft to thefan shaft through the planet carrier.

The differential gearbox assembly of any preceding clause, the input ofthe electric machine assembly being coupled to the planet carrier, andthe electric machine assembly drives the planet carrier to providemechanical power to the fan shaft.

The differential gearbox assembly of any preceding clause, the electricmachine assembly generating electric power from the differential gearboxassembly.

The differential gearbox assembly of any preceding clause, the electricmachine assembly being an annular drive system such that the electricmachine assembly is annular about the drive shaft

The differential gearbox assembly of any preceding clause, the electricmachine assembly including a stator and a rotor that are annular rings.

The differential gearbox assembly of any preceding clause, the statorand the rotor being annular about the drive shaft.

The differential gearbox assembly of any preceding clause, the electricmachine assembly being a compact drive system.

The differential gearbox assembly of any preceding clause, the compactdrive system including a stator and a rotor disposed within a housing ofthe electric machine assembly.

The differential gearbox assembly of any preceding clause, the electricmachine assembly including an electric generator that generates electricpower from the epicyclic gear assembly when mechanical power of the fanshaft is reduced.

The differential gearbox assembly of any preceding clause, the electricmachine assembly including an electric motor that provides mechanicalpower to the fan shaft through the differential gearbox assembly in afirst operating mode of the turbine engine. The electric generatorgenerates the electric power in a second operating mode of the turbineengine.

The differential gearbox assembly of any preceding clause, the electricmachine assembly including an electric motor for driving at least onegear of the differential gearbox assembly and an electric generator forgenerating electric power.

The differential gearbox assembly of any preceding clause, the input ofthe electric machine assembly being coupled to the ring gear. Theelectric machine assembly drives the ring gear to provide mechanicalpower to the fan shaft.

The differential gearbox assembly of any preceding clause, the electricmachine assembly including a stator and a rotor that includes one ormore permanent magnets on the ring gear. The stator connects to a staticcomponent of the differential gearbox assembly.

The differential gearbox assembly of any preceding clause, the electricmotor being coupled to the ring gear.

The differential gearbox assembly of any preceding clause, the electricgenerator being coupled to the drive shaft.

The differential gearbox assembly of any preceding clause, the electricmachine assembly being coupled to the planet carrier. The electricmachine assembly drives the planet carrier to provide mechanical powerto the fan shaft.

The differential gearbox assembly of any preceding clause, a torque onthe ring gear being split between the booster shaft and the electricmachine assembly.

The differential gearbox assembly of any preceding clause, a torque drawof the electric machine assembly being increased when a torque draw of abooster of the turbine engine is reduced.

The differential gearbox assembly of any preceding clause, the boosterincluding a plurality of variable stator vanes movable about a pitchaxis to change an incidence angle of the plurality of variable statorvanes.

The differential gearbox assembly of any preceding clause, the pluralityof variable stator vanes being actuated to change the torque draw of thebooster.

The differential gearbox assembly of any preceding clause, a booster ofthe turbine engine including a first booster stage connected to the ringgear and a second booster stage connected to the drive shaft.

The differential gearbox assembly of any preceding clause, the boostershaft, the drive shaft, and the fan shaft rotating at different speedsthrough the differential gearbox assembly.

The differential gearbox assembly of any preceding clause, the fan shaftincluding a first fan shaft and a second fan shaft. The first fan shaftconnects to the planet carrier and the second fan shaft connects to thering gear.

The differential gearbox assembly of any preceding clause, the driveshaft being a low pressure (LP) shaft.

A turbine engine including a turbine, a fan, and a differential gearboxassembly. The turbine includes a drive shaft. The fan includes a fanshaft. The differential gearbox assembly includes an epicyclic gearassembly coupling the fan shaft to the drive shaft. The epicyclic gearassembly includes a sun gear, a planet gear constrained by a planetcarrier, and a ring gear. The sun gear, the planet gear, and the ringgear all rotate about the drive shaft. The differential gearbox assemblyincludes and an electric machine assembly. The electric machine assemblyincludes an input coupled to the epicyclic gear assembly. The electricmachine assembly provides mechanical power to the fan through theepicyclic gear assembly.

The turbine engine of the preceding clause, further including a booster.The booster includes a booster shaft. The ring gear is coupled to thebooster shaft. The differential gearbox assembly splits a torque betweenthe booster shaft and the electric machine assembly.

The turbine engine of any preceding clause, the differential gearboxassembly transferring a torque from the drive shaft to the electricmachine assembly.

The turbine engine of any preceding clause, the differential gearboxassembly transferring the torque from the drive shaft to the fan shaftthrough the planet carrier.

The turbine engine of any preceding clause, the input of the electricmachine assembly being coupled to the planet carrier, and the electricmachine assembly drives the planet carrier to provide mechanical powerto the fan shaft.

The turbine engine of any preceding clause, the electric machineassembly generating electric power from the differential gearboxassembly.

The turbine engine of any preceding clause, the electric machineassembly being an annular drive system such that the electric machineassembly is annular about the drive shaft.

The turbine engine of any preceding clause, the electric machineassembly including a stator and a rotor that are annular rings.

The turbine engine of any preceding clause, the stator and the rotorbeing annular about the drive shaft.

The turbine engine of any preceding clause, the electric machineassembly being a compact drive system.

The turbine engine of any preceding clause, the compact drive systemincluding a stator and a rotor disposed within a housing of the electricmachine assembly.

The turbine engine of any preceding clause, the electric machineassembly including an electric generator that generates electric powerfrom the epicyclic gear assembly when power of the fan shaft is reduced.

The turbine engine of any preceding clause, the electric machineassembly including an electric motor that provides mechanical power tothe fan shaft through the differential gearbox assembly in a firstoperating mode of the turbine engine. The electric machine assemblygenerates the electric power in a second operating mode of the turbineengine.

The turbine engine of any preceding clause, the electric machineassembly including an electric motor for driving at least one gear ofthe differential gearbox assembly and an electric generator forgenerating electric power.

The turbine engine of any preceding clause, the electric machineassembly being coupled to the ring gear. The electric machine assemblydrives the ring gear to provide mechanical power to the fan shaft.

The turbine engine of any preceding clause, the electric machineassembly including a stator and a rotor that includes one or morepermanent magnets on the ring gear. The stator couples to a staticcomponent of the differential gearbox assembly.

The turbine engine of any preceding clause, the electric motor beingcoupled to the ring gear.

The turbine engine of any preceding clause, the electric motor beingcoupled to the ring gear.

The turbine engine of any preceding clause, the electric generator beingcoupled to the drive shaft.

The turbine engine of any preceding clause, the electric machineassembly being coupled to the planet carrier. The electric machineassembly drives the planet carrier to provide mechanical power to thefan.

The turbine engine of any preceding clause, a torque on the ring gearbeing split between the booster shaft and the electric machine assembly.

The turbine engine of any preceding clause, a torque draw of theelectric machine assembly being increased when a torque draw of thebooster is reduced.

The turbine engine of any preceding clause, the booster including aplurality of variable stator vanes movable about a pitch axis to changean incidence angle of the plurality of variable stator vanes.

The turbine engine of any preceding clause, the plurality of variablestator vanes being actuated to change a torque draw of the booster.

The turbine engine of any preceding clause, the booster including afirst booster stage coupled to the ring gear and a second booster stageconnected to the drive shaft.

The turbine engine of any preceding clause, the booster shaft, the driveshaft, and the fan shaft rotating at different speeds through thedifferential gearbox assembly.

The turbine engine of any preceding clause, the fan including a firstfan having a first fan shaft and a second fan having a second fan shaft.The first fan shaft couples to the planet carrier and the second fanshaft couples to the ring gear.

The turbine engine of any preceding clause, the drive shaft being a lowpressure (LP) shaft.

A method of operating a differential gearbox assembly for a turbineengine including a fan having a fan shaft, a turbine having a driveshaft, and a booster having a booster shaft. The method includestransferring torque through the drive shaft from the turbine to a sungear of the differential gearbox assembly, transferring the torque fromthe sun gear through a planet carrier of the differential gearboxassembly to the fan shaft. The fan shaft is connected to and rotates thefan. The method includes transferring the torque from the sun gearthrough a ring gear of the differential gearbox assembly to the boostershaft. The method includes splitting the torque between the boostershaft and an electric machine assembly.

The method of the preceding clause, the booster shaft, the fan shaft,and the drive shaft rotating at different speeds.

The method of any preceding clause, further including driving the ringgear with the electric machine assembly to control a distribution of thetorque between the booster shaft and the fan shaft.

The method of any preceding clause, further including driving the planetcarrier with the electric machine assembly to control a distribution ofthe torque between the booster shaft and the fan shaft.

The method of any preceding clause, further including providingmechanical power from the electric machine assembly to the differentialgearbox assembly in a first operating mode of the turbine engine.

The method of any preceding clause, further including generatingelectric power at the electric machine assembly in a second operatingmode of the turbine engine.

The method of any preceding clause, further including providingmechanical power from the electric machine assembly to the fan shaftthrough the differential gearbox assembly.

The method of any preceding clause, further including generatingelectric power by the electric machine assembly when mechanical power tothe fan is reduced.

The method of any preceding clause, further including reducing thetorque to the booster shaft and increasing the torque to the electricmachine assembly.

The method of any preceding clause, the reducing the torque to thebooster shaft including actuating a plurality of variable stator vanesto reduce the torque to the booster shaft.

Although the foregoing description is directed to the preferredembodiments of the present disclosure, other variations andmodifications will be apparent to those skilled in the art and may bemade without departing from the spirit or the scope of the disclosure.Moreover, features described in connection with one embodiment of thepresent disclosure may be used in conjunction with other embodiments,even if not explicitly stated above.

1. A differential gearbox assembly for a turbine engine having a fanshaft, a drive shaft, and a booster having a plurality of variablestator vanes and a plurality of blades coupled to a booster shaft, thedifferential gearbox assembly comprising: an epicyclic gear assemblycoupling the fan shaft to the drive shaft and coupling the booster shaftto the drive shaft through the epicyclic gear assembly, the epicyclicgear assembly including a sun gear, a planet gear constrained by aplanet carrier, and a ring gear, the sun gear coupled to the driveshaft, the planet carrier coupled to the fan shaft, and the ring gearcoupled to the booster shaft, wherein the sun gear, the planet gear, andthe ring gear all rotate about the drive shaft, and the drive shaftprovides mechanical power to the fan shaft and to the booster shaftthrough the epicyclic gear assembly; and an electric machine assemblycomprising an input coupled to the epicyclic gear assembly, the electricmachine assembly providing mechanical power to the fan shaft through theepicyclic gear assembly, wherein the electric machine assembly includesan electric motor and an electric generator for generating electricpower, the electric motor providing additional mechanical power to thefan shaft during operation of the turbine engine, and at least a portionof the mechanical power from the drive shaft is provided to the electricgenerator when mechanical power to the fan shaft is reduced such thatthe electric generator generates electric power from the epicyclic gearassembly, and the plurality of variable stator vanes are actuated tochange an incidence angle of the plurality of variable stator vanes tochange an air flow to the plurality of blades of the booster such that aspeed of the ring gear remains constant while the electric motorprovides the additional mechanical power to the fan shaft.
 2. Thedifferential gearbox assembly of claim 1, wherein the differentialgearbox assembly splits a torque between the booster shaft and theelectric machine assembly.
 3. The differential gearbox assembly of claim1, wherein the electric motor drives at least one gear of the epicyclicgear assembly.
 4. The differential gearbox assembly of claim 1, whereinthe input of the electric machine assembly is coupled to the planetcarrier, and the electric machine assembly drives the planet carrier toprovide mechanical power to the fan shaft.
 5. The differential gearboxassembly of claim 1, wherein the electric machine assembly is an annulardrive system such that the electric machine assembly is annular aboutthe drive shaft.
 6. The differential gearbox assembly of claim 1,wherein the electric machine assembly is a compact drive system. 7.(canceled)
 8. The differential gearbox assembly of claim 1, wherein theelectric motor provides mechanical power to the fan shaft through thedifferential gearbox assembly in a first operating mode of the turbineengine, and the electric generator generates the electric power in asecond operating mode of the turbine engine.
 9. The differential gearboxassembly of claim 1, wherein the input of the electric machine assemblyis coupled to the ring gear, and the electric machine assembly drivesthe ring gear to provide mechanical power to the fan shaft.
 10. Thedifferential gearbox assembly of claim 9, wherein the electric machineassembly comprises: a stator connected to a static component of thedifferential gearbox assembly; and a rotor that includes one or morepermanent magnets on the ring gear.
 11. A turbine engine comprising: aturbine including a drive shaft; a fan including a fan shaft; a boosterincluding a booster shaft, a plurality of variable stator vanes, and aplurality of blades coupled to the booster shaft; and a differentialgearbox assembly comprising: an epicyclic gear assembly coupling the fanshaft to the drive shaft and coupling the booster shaft to the driveshaft through the epicyclic gear assembly, the epicyclic gear assemblyincluding a sun gear, a planet gear constrained by a planet carrier, anda ring gear, the sun gear coupled to the drive shaft and the planetcarrier coupled to the fan shaft, and the ring gear coupled to thebooster shaft, wherein the sun gear, the planet gear, and the ring gearall rotate about the drive shaft, and the drive shaft providesmechanical power to the fan shaft and to the booster shaft through theepicyclic gear assembly; and an electric machine assembly comprising aninput coupled to the epicyclic gear assembly, the electric machineassembly providing mechanical power to the fan through the epicyclicgear assembly, wherein the electric machine assembly includes anelectric motor and an electric generator for generating electric power,the electric motor providing additional mechanical power to the fanshaft during operation of the turbine engine, and at least a portion ofthe mechanical power from the drive shaft is provided to the electricgenerator when mechanical power to the fan shaft is reduced such thatthe electric generator generates electric power from the epicyclic gearassembly and the plurality of variable stator vanes are actuated tochange an incidence angle of the plurality of variable stator vanes tochange an air flow to the plurality of blades of the booster such that aspeed of the ring gear remains constant while the electric motorprovides the additional mechanical power to the fan shaft.
 12. Theturbine engine of claim 11, wherein the differential gearbox assemblysplits a torque between the booster shaft and the electric machineassembly.
 13. The turbine engine of claim 11, wherein the electric motordrives at least one gear of the epicyclic gear.
 14. The turbine engineof claim 11, wherein the input of the electric machine assembly iscoupled to the planet carrier, and the electric machine assembly drivesthe planet carrier to provide mechanical power to the fan shaft.
 15. Theturbine engine of claim 11, wherein the electric machine assembly is anannular drive system such that the electric machine assembly is annularabout the drive shaft.
 16. The turbine engine of claim 11, wherein theelectric machine assembly is a compact drive system.
 17. (canceled) 18.The turbine engine of claim 11, wherein the electric motor providesmechanical power to the fan shaft through the differential gearboxassembly in a first operating mode of the turbine engine, and theelectric generator generates the electric power in a second operatingmode of the turbine engine.
 19. The turbine engine of claim 11, whereinthe input of the electric machine assembly is coupled to the ring gear,and the electric machine assembly drives the ring gear to providemechanical power to the fan shaft.
 20. The turbine engine of claim 19,wherein the electric machine assembly comprises a stator connected to astatic component of the differential gearbox assembly and a rotor thatincludes one or more permanent magnets on the ring gear.
 21. Thedifferential gearbox assembly of claim 1, wherein the plurality ofvariable stator vanes are actuated to change the incidence angle of theplurality of variable stator vanes to reduce mechanical power to thebooster shaft such that the electric generator generates electric powerfrom the epicyclic gear assembly.
 22. The differential gearbox assemblyof claim 8, wherein the first operating mode and the second operatingmode include at least one of a takeoff flight mode, a climb flight mode,a cruise flight mode, a step change flight mode, a descent flight mode,a landing flight mode, or a taxi flight mode, and the second operatingmode is different than the first operating mode.